Recent research has established that a complex system exists in human saliva which plays an important role in the maintenance, protection and repair of the dental enamel. The key feature of this protective system is the presence, in the saliva, of supersaturated, but stabilized concentrations of calcium and phosphate ions. This stabilization is maintained by at least two unusual salivary macromolecules, which act by inhibiting precipitation of calcium phosphate salts from the supersaturated saliva. A further part of this system consists of a thin film of selectively absorbed salivary proteins, known as the acquired enamel pellicle, which is present on all enamel surfaces, and which prevents the deposition of calcium phosphate minerals from the supersaturated saliva on to the teeth. This system provides important protection against dental caries, by suppressing enamel dissolution and mineral transport during carious attack, and by recalcifying at least some early carious lesions. Also, microbiological degradation of the inhibitory macromolecules, appears to be a factor in calculus formation, and therefore important in periodontal disease. The purpose of the proposed research is to identify and characterize the salivary precipitation inhibitors, and to determine their mode of action. From this research will come an improved understanding of the relationships which exist between the dental enamel and the oral environment, in both health and disease.